Sound record and its production



March 29, 1938. J. o. KLEBER 2,112,699

SOUND RECORD AND ITS PRODUCTION Filed April 10, 1937 Rectifier INVENTORJAcKso v 0. KLEBER A iromwz? Patented Mar. 29, 1938 UNITED STATES ATENTOFFICE 3 Claims.

This invention relates to sound records and their production under thecontrol of electric currents varying in accordance with sound.

When a sound record of the laterally or the 5 perpendicularly undulatingtype is produced in the form of a spiral sound track of varyingeffective width and with turns of the track concentrated very closetogether, the large undulations tend to over-cut, that is, theundulations in one turn of the sound track groove tend to cut into anadjacent turn of the groove, or to objectionably weaken the wall ofmaterial separating adjacent turns of the groove, so that when the soundis reproduced, the stylus on passing the over-cu place, may jump backinto or cut across into the same turn it has just played, thus repeatingthe sound in this one turn, without progressing beyond it. The pitch ofthe spiral must, therefore, be large enough to furnish adequate freespace for the widest parts of the sound track where the largestundulations are recorded.

When the groove is too shallow, the reproducing stylus may be subject toa difficulty known as failure to track, and may have a tendency to jumpentirely out of the track it should follow, thus interrupting thecontinuity of reproduction of the sound, particularly when theundulations are very large. The undulations, when large. 0 exert agreater force on the reproducing stylus than when small, the frequencybeing the same in both cases. If the groove is too shallow, the smallamount of material in the Wall of the groove, required to force thestylus into vibration, cannot stand the strain and becomes too rapidlyworn to retain its undulations in their original form, or becomesstrained out of shape, or the stylus may actually out across theundulations, in short-cut fashion, without following the detailedcontour of the undulations, thus introducing objectionable sounddisturbances and distortion, and mutilating the record. In order torecord the undulations properly, therefore, the

usual practice requires that throughout the length 1 of the groove, theconstant average depth of the groove be made large enough to insure thatthe reproducing stylus can not suffer a failure to track at places wherethe undulations are largest.

m) Another difficulty, called echo, is also experienced when the groovesare packed too close together. By echo is meant an effect produced bythe sound recorded in one groove upon the reproduction of sound from anadjacent 5 groove. When the grooves are so close or the undulations areso large that the wall of material separating two adjacent groovesbecomes very thin, the material becomes so deformed or weakened by theundulations and by the reproducing stylus, that the undulations in onegroove control to some extent the vibrations of the stylus in anadjacent groove. Objectionable distortion and disturbance of theoriginal characteristics of the sound may thus be produced.

One object of the present invention, is to overcome one or more of thedifficulties referred to above.

Another object is to produce a concentrated sound record adapted formanufacture at low cost and capable of reproducing sound with highfidelity.

Another object is to concentrate a sound record to a greater extent thanis ordinarily possible without introducing disturbances or distortioninto the sound reproducible from the record.

Another object is to provide a method of and means for efficientlyproducing sound records of the kind referred to.

In accordance with one aspect of the present invention, a sound trackhaving an envelope of variable width, is produced in response to soundcurrents and is traced in such directions on the surface of the recordblank, that a plurality of similarly directed portions thereof in serieswith each other are positioned laterally close together in a compact rowfor the purpose of concentrating the record within a small space. Theselaterally adjacent portions of the track may constitute turns in aspiral and may be so close to each other as to approach but not quitereach the point of appreciable or substantial interference. When theamplitude of the sound currents and of the undulations recorded in oneportion of the track exceeds a. predetermined limit beyond which thisportion might tend to interfere with another laterally adjacent portion,the direction of the track is changed to increase the spacing betweenthe center lines of these portions sufiiciently to dodge and avoidobjectionable interference.

After the sound current amplitude decreases to less than thepredetermined value, the direction of the track is changed back toreduce the unused waste space between the laterally adjacent portions ofthe track. A delay is preferably provided after the decrease ofamplitude and before the track direction is changed, to avoid thepossible objectionable effect of too sudden restoration of the directionwhen the amplitude fluctuates rapidly between very large and smallvalues.

By increasing the average depth of the sound track groove when theundulations increase from less to more than a predetermined amplitudeand by decreasing the average depth after the undulations decrease frommore to less than this predetermined amplitude, the small amplitudeundulations make a narrower track than if the average depth weremaintained constantly sufficient for the largest undulations, andconsequently, portions of the track containing undulations of smallamplitude may be packed more closely together without interference.

Provision is made for independently controlling the direction of thesound track groove and the depth of the groove, and for the manual orautomatic control of both direction and depth in response to changes ofamplitude of the sound current being recorded, thus permittingefficiently of a high degree of concentration of the record.

These and other objects and features of the invention will be understoodin further detail by reference to the accompanying drawing and thedetailed description and claims which follow.

It will be understood that the words sound track, as used herein, whenapplied to a groove, refer not only to the configuration of the surfacewithin the groove, but also to the modification of the metallic ornon-metallic plastic material of the blank by the recording orreproducing stylus within the region inside or outside of the actualgroove, as it affects the reproduction of sound from the record.

In the drawing, Fig. 1 is a schematic circuit diagram showing one formof apparatus adapted to produce sound records according to the presentinvention.

Fig. 2 is a fragmentary plan view of a record adapted to be made by theapparatus of Fig. 1, and showing exaggerated spacings between tracks forthe purpose of clearness.

Fig. 3 shows an enlarged section of a portion of the record, taken onthe line 33, Fig. 2.

In Fig. 1, the sound record blank I, is in the form of a disk of wax,soft metal, such as aluminum, or other well known suitable plasticmaterial. The horizontal table 2 is fast to the vertical shaft 3, theupper end of which projects through the central hole 4 of the disk I,see Fig. 2. The table and shaft provide a holder for supporting the diskhorizontally and for rotating it around its central axis. The shaft 3 isrotated at constant speed by the electric motor 5 which may includegearing, not shown, to suitably reduce the speed of shaft 3. Current foroperating the motor 5 is supplied over wires 6, I from the source ofpower 8 by closure of the switch 9, and the motor speed may be adjustedby the rheostat I0, unless the motor be of the synchronous typeenergized from an alternating current source.

The recording stylus II is supported by the recording head I2, supportedon the tone arm l3,

which in turn is rotatable on a horizontal axis on the pivot I4 and maybe balanced to any desired extent by the fixed counterweight I5 with thescrew I6 serving as an adjustable counterweight. The pivot I4 issupported by and held in fixed relation to the carriage II, mounted onthe wheels I8, rolling on the track I9 which guides the carriage I1 andthe stylus II in a path along a radius of the disk I and the table 2.

The carriage I1 is moved radially inward toward the shaft 3 by rotationof the screw 20, engaging with the threaded nut section 2|, supportedfrom the carriage and hinged relatively thereto on the pivot 22, so thatthe nut section may be swung away from meshing contact with the threadsof screw 28 to permit of movement of the carriage independently of thescrew.

The screw shaft 20 is rotated by the constant speed electric motor 24which may include gearing, not shown, for suitably reducing the speed ofthe screw 20 below the speed of the motor shaft 25. The circuit forsupplying power to the motor 24 may be traced from the source 8, throughswitch 9, conductors 6 and 26, motor 24, conductor 21, rheostat 28,sliding contact 29, and back to source 8 through conductor I. Adjustmentof rheostat 28 changes the constant speed of motor 24.

The advance ball 30 guides the stylus I I in relation to the upper orhorizontal surface of the blank I, while the stylus cuts a spiral groovein this surface due to the circular movement of the blank while thestylus is fed radially or, in other words, laterally of the circularpath of movement of the blank. The ball 30 is secured in the lower endof the rod 3|, held between the guiding rollers 32, supported from thearm I3. The rod 3| is held in a fixed position vertically by the screwshaft 33 which in turn is supported by the motor 34, supported on thearm I3. The motor 34 has the circuit 84, 85 for rotating the shaft 33 inone direction and the circuit 85, 96, for rotating it in the oppositedirection. The threads of screw 33 mesh with the threaded end of thecross arm 35, fastened to the rod 3|. Rotation of screw 33 by motor 34,adjusts the vertical position of rod 3|, and ball 38 relatively to thestylus The screw I6 is ordinarily adjusted to unbalance the arm I3 insuch a direction as to press the ball 30 and stylus toward the blank Iwith suitable pressure to insure maintenance of;

the desired position of the stylus point relatively to the surface ofthe blank to control the average depth of groove being cut by thestylus.

Sound waves to be recorded are impressed on the microphone 36, producingelectric currents which may be increased to suitable amplitude by theadjustable amplifier 31, from the output of which the amplified soundcurrents are transmitted to the recording head I 2, including with othersuitable elements, the coil 38 or some other well known type of motorelement for vibrating the stylus in accordance with the sound currents.The recording head I2 may be of the type in which vibrations of thestylus II produce perpendicular undulations on the blank or of the typeproducing lateral undulations thereon.

The rectifier 39, connected in parallel with the recording coil 38,converts the alternating sound currents into pulsating direct current ofchanging value corresponding approximately with the changes of amplitudeor intensity of the sound currents.

The potentiometer 40 in the output circuit of the rectifier 39 isconnected in the input of amplifier 4|, and is adjusted to control theamplification of the direct current variations to the desired degree.The output circuit of amplifier 4| includes the electromagnetic relay 42which has the armature 43, normally retracted by the spring 44. A lowresistance short circuited ring 45, surrounding the armature end of thecore of relay 42, is adjusted to allow armature 43- to attract promptlywhen the current energizing the relay increases to more than apredetermined value, and to cause 43, after the current energizing therelay decreases suddenly to less than said predetermined value.

The delay in restoration of relay 42 to normal should be long enough toavoid reduction of the track spacing when the decrease of currentamplitude is very brief, or when there are rapid fluctuations from largeto small and back to large amplitudes. In a given case, for example, therelay 42 may be designed and adjusted in well known manner, to provide adelay equal to that of one half or a whole rotation of the blank I.Ordinarily the delay should not be less than about one-tenth of asecond, since a much briefer delay may have a tendency to introduceundesired audio frequency distortion components in the secondreproducible from the track.

When the energizing current increases to more than the predeterminedvalue capable of actuating relay 42, the armature 43 first contacts withspring 56, and many remain in contact therewith without beingsufficiently attracted to establish contact with spring 47, unless thecurrent increases to a substantially greater value.

Contacts 48 and 46 connect, respectively, with the sliders 29 and SI ofthe rheostat 28 and bridge these sliders when closed, while contact 47connects with the slider 52, so that closure of contacts 53,46, 41,short-circuits the rheostat between the sliders 29 and 52.

The contacts of push button 53 are connected in parallel with contacts43, 46, and those of push button 5 3 in parallel with contacts 43, 47,so that the same changes in rheostat 28 can be made manually by the pushbuttons 53, 54, as are made automatically by the relay 42.

The shaft of the motor 24 has the speed responsive governor 10 of wellknown form, having the collar TI, fast to the shaft, and the collar I2,having the bearing on the shaft permitting it to slide freely axially ofthe shaft,'and having a hollow stem I3 projecting therefrom. Leafsprings I4 are fastened at their ends to collars TI I, 72, respectively,between which they are bridged with a very slight curvature radiallyoutward from shaft 25. Weights 75, secured to springs I4 half waybetween their ends, move radially outward by centrifugal force whenshaft 25 rotates, thus causing stem 13 to move to the right.

The insulating handle "I8 is normally pressed to the right against therounded free end of stem 13 by the contact spring IT, on which thehandle I6 is supported. Outward bowing of the springs 74, permits thehandle Iii tobe moved manually to the right. When handle I5 is movedsufiiciently to the right, either manually or by speeding up of motor 24to more than some predetermined speed, spring I! breaks contact withspring I8 and makes contact with spring I9, thereby closing a circuitfor motor 34, traced from the power source 8, through switches 9 and8E], springs 'I'i, l9, conductor 8! to spring 82 which is under tensionmaking it contact withspring 83 when arm 35 is in its lowest positionrelatively to arm I3, then through the upper circuit 8 85 of motor 34,through the rheostat 86 for regulating the speed of motor 34, andthrough lead 7 back to the source 8. Current through circuit M, 85causes motor 34 to rotate screw 33 in a direction to move arm 35 upwardrelatively to arm I3, thus lowering arm I3 and stylus I I relatively tostem 3i advance ball 30, and the record blank I, thereby causing thestylus to cut a deeper groove in the blank.

When arm 35 moves from its low-estto its highest position relatively toarm I3, the insulation 90, carried by arm 35, pushes spring 83 upwardout of contact with spring 82, thus stopping rotation of the motor 34,while insulation 9I carried by arm 35, moves up and allows the upwardlyten.- sioned spring 92 to make contact with spring 93.

When handle 16 is again moved to the left, as shown in the drawing,while contacts 92, 93 are closed, a circuit may be traced for motor 34,from the source 8, through switches 9, 8B, springs 11, 1'8, lead 94,spring 93, 92, circuit 96, 85 of motor 34, rheostat 86, and back throughlead I to source 8. Current through this circuit causes the motor 3 5 torotate screw 33 in a direction to move arm 35 downward relatively to armI3, thus raising the arm I3 and stylus I I relatively to the advanceball and the blank I, and thereby causing the stylus to cut a moreshallow groove. When the arm moves from its. highest to its lowestposition relatively to arm I3, the insulation 90 moves down and allowsspring 83 to re-establish contact with spring 82, while insulation 9|moves down and causes spring 92 to break contact with spring 93, asshown in Fig. 1, thus stopping rotation of motor 34.

When recording sound, the switch 9 is closed to rotate motors 5 and 24and cause the stylus I I to cut the groove 60, Figs. 2 and 3, along aspiral path on the upper surface of the blank I. For the purpose ofclearness, the spacings between the series turns GI, 62, 63, 64, 65, 66,61, I58, of the spiral are considerably magnified or exaggerated in thedrawing, to avoid overlapping of the lines representing the closestturns, and to show the other turns of the track with relatively largerspacings. The size of groove 60, Fig. 3 is also exaggerated to show itsform more clearly.

The form of the groove, shown in Fig. 3 for the purpose of illustration,has an ordinary V-shaped section with an angle of about 90 degreesbetween its arms. The bottom of the V is rounded in the usual mannerwith a circular shape.

The profile of the section corresponds with that of the cutv ting edgeof the stylus. The radius of curvature of the bottom of the V may beabout .002 of an inch, for example. It will be seen that a sound trackmade with this type of groove, has an envelope of varying width, whetherthe sound is recorded as perpendicular or as lateral undulations.

Sound recorded as perpendicular undulations, produces .a groove havingtwo edges, each of which contains undulations consisting of lateraldisplacements in opposite directions at opposite edges of the groove,while sound recorded as lateral undulations, produces a groove havingundulations in each edge consisting of lateral displacements in the samedirection at opposite edges of the groove. The resulting envelopes ofthe undulations vary in width with changes of amplitude of theundulations. Consequently the narrow strip representing the area betweenthe outer envelopes of the undulations at opposite edges of the groove,increases in width as the amplitude of the sound current increases, andthis area enoroaches more and more on the area between turns of thespiral track. Since the spacing between turns is limited by the closepacking of the turns, it is possible with any given spacing to recordonly those soundshaving less than a predetermined amplitude withoutrisking objectionable interference with a portion of the sound track ina laterally adjacent turn.

The amplifier 31 is adjusted to supply sound currents :of suitableamplitude'to coil 38 to vibrate stylus 'l I adequately for recording theweakest components to be reproduced. The constant speedof motor 5 isadjusted by slider 29 of rheostat 28, to feed stylus ll radially of theblank I niodate still larger undulations.

at the desired speed relatively to the circular speed of the blank, toprovide the desired constant spacing between turns .of the spiral. Thedesired spacing may be determined in part by the character of the soundrecorded. If the char- .acter is such that the amplitude remains at a"relatively small value most of the time and there are only a few trainsof undulations of much largeramplitude, the turns may be packed veryclosetogether'for the low amplitudes.

For a highly concentrated record, the potentiometer 40 is adjusted sothat relay 42 will close contacts 43, 36 as soon as the sound currentsexceed the predetermined amplitude chosen as the largest valuerecordable without interference at, the desired smallest spacing betweenturns. Instruments, not shown, may be provided to indicate visually thecurrent in the various parts of the circuit to facilitate adjustments ofthe circuit, but it will be understood that such instru- .ments are notessential.

Closure of contacts 43, 46 speeds up rotation of 'motor 24, thusincreasing the rate of radial feed of stylus II and widening the spacingbetween the center lines of any two laterally adjacent portions of, thetrack. Closure of contacts 46, 41, still further increases the spacingto accom- Adjustment of sliders 5!, 52 control the amount of increase inspacing between turns of the track corresponding with the successiveattracted positions of armature 43. Additional contacts and motor speedadjustments, not shown, may be similarly provided for relay 42. The ring45 on relay 42 causes a delay in the opening of contacts 46, 41, similarto the delay described in connection with the opening of contacts 43,46.

The undulations recordable in the closest turns of the spiral are ofsuch small amplitude that they do not require the depth of groove neededfor larger amplitudes, and consequently the width of the groove andtherefore of the sound track may be less than for the larger amplitudes,in contrast with the usual practice where the depth of groove,throughout its length, is kept large enough to handle large amplitudes..Appreciable space may thus be saved by the present invention.

The governor 10 is preferably so adjusted that when the sound amplitudeincreases enough to operate relay 42, the corresponding increase ofspeed of motor 24 causes spring 11 to move to the right. When switch 80is closed and spring 11 .makes contact with spring 19, the stylus II ismoved down to cut a deeper groove which can be made of sufficient depthto handle adequately the undulations of increased amplitude.

The sound at the beginning of the record, Figs. 2 and 3, is below thepredetermined amplitude necessary to cause actuation of relay 42, andthe turns 6|, 62, 63, 64 and part of 65, may be con- At the point I onthe sound track, the amplitude of the sound currents and of theundulations has exceeded the predetermined value necessary to actuaterelay 42, and contacts 43, 46 have closed to cut out section 29, ofrheostat 28, thereby speeding up motor 24 and increasing the rate ofdisplacement of the sound track laterally of the circular path ofmovement of the blank, per unit angle measuredaround the axis ofrotation, or in other words, increasing the spacing between turns of thespiral so that a larger space is now available for recording the largerundulations without interference.

The motor 24 continues to rotate at the higher speed up to the point IOIon the sound track, when the current suddenly decreases to a smallamplitude below that necessary to maintain actuation of relay 42, butthe relay remains actuated, owing to the ring 45, and consequently motor24 maintains its higher speed until the point 02 is reached, whencontacts 43, 46 open. Motor 24 then slows-down to the minimum speed andproduces the minimum spacing between turns 61, 68, 69. The abovedescribed steps may be repeated many times during the production of asingle record.

By closing switch 80, the circuit of motor 34 and the associatedapparatus is efiective auto matically to increase the average depth ofthe groove 60 when the amplitude of sound currents changes from below toabove the predetermined value sufficient to actuate relay 42, and iseffective automatically toreduce the average depth of groove when thesound currents decrease from above to below this predetermined value.

When the point 100 is reached on the blank I, the speed of motor 24 issufiicie'nt to open contacts 11, 18 and close contacts 11, 19, thuscausing the operation of motor 34 .to increase the average depth ofgroove, as shown by the deeper groove 65, 66 in Fig. 3. Since the depthof groove is not increased until after the radial feed speed of thestylus H is increased by motor 24, there is less tendency forinterference resulting from increase of groove width before the spacingbetween turns increases, than if the depth increase occurred withoutthis delay.

At the point I02, when the relay 42' releases and the speed of motor 24decreases, the contacts 11, 19 open and contacts 11, 18 close to Operatemotor 34 to decrease the average depth of groove, as shown by theshallower groove 61, 68, 69 Fig. 3. By means of the method and apparatusdescribed,

the average depth of the groove and consequently the effect of groovedepth on the width may be kept to a minimum.

Concentration of the sound track by controlling the pitch of the spiraland the average depth of the groove, either independently or together,as referred to above, results in a concentration of sound tracksconsiderably in excess of that of prior records having a spiral ofconstant pitch and a groove of constant average depth throughout itslength. This concentration is obtained without incurring thedifficulties referred to above in connection with prior records.

Records produced by the above described methods are adapted forreproduction by the usual equipment, not shown, for reproducing soundfrom ordinary disk records. The reproducing pick up, such as a stylusfor example, follows and is guided by the sound track in the directionin which it was recorded.

The method, described above, of changing the spacing between laterallyadjacent portions. of sound tracks, is useful not only for the closestpacked tracks, but is also advantageously applicable to much largerpredetermined spacings Where space in excess of the predetermined amountis to be conserved.

If desired, the average depth of the groove may be adjusted to anydesired value by manual operation of the switch handle 16. The switch 89may then be opened and the record produced while automaticallycontrolling the pitch of the spiral by relay 42, without automaticallycontrolling the depth of the groove.

It will be understood that the dimensions and shape of the groove andstylus, the amount of spacing between laterally adjacent portions of thetrack, the geometrical shape of the blank and of the path of the track,and even the type of sound track and blank, are susceptible toconsiderable departure from the specific details of the embodimentschosen as illustrations of the invention, Without actually departingfrom the invention itself in its broader aspects as dis.- closed andclaimed herein.

Iclaim: l:"'

l. A sound record having a record surface arranged for rotation in acircular path and having a sound track groove on said surface disposedspirally around the axis of rotation, said groove containing a sectionhaving a predetermined average depth and having undulations of less thana predetermined amplitude and having a predetermined rate ofdisplacement laterally of said circular path per unit angle measuredaround said axis, and another section of said groove having more thansaid predetermined average depth and having undulations of more thansaid predetermined amplitude and having a greater rate of lateraldisplacement per unit angle than said first mentioned rate.

2. The method of recording sound on a record blank, which comprisesproducing a sound track groove on the surface of the blank in responseto sound currents, causing said track to be traced in such a directionas to produce in series a plurality of similarly directed portionslaterally disposed close to each other, and changing the direction andaverage depth of the groove in response to predetermined changes in theamplitude of said currents.

3. Apparatus for recording sound on a record blank, including arecording stylus, a holder for supporting the blank in recordingrelation to said stylus, means for producing relative motion betweensaid holder and said stylus in such directions that the stylus traces onthe blank a sound track groove having in series a plurality of similarlydirected portions disposed so close to each other laterally as toapproach interference, a circuit for sound currents, means responsive tocurrent in said circuit for imparting to said stylus the vibrations tobe recorded and for producing undulations in the sound track within anarrow area of varying Width on the surface of the blank, means forchanging the average depth of said groove, means for changing thedirection of the sound track, and means responsive to predeterminedchanges of current in said circuit for controlling the operation of saiddepth and direction changing means.

' JACKSON 0. KLEBER.

CERTIFICATE OF CORRECTION. Patent No. 2,112,699 March 29, 19

JACKSON 0. KLEBER.

It is hereby certified that error appears in the printed. specificationof the above mmhered patent requiring correction as follows: Page 5,first column, line Z for the word "many" read my; and that the saidLetters Patent shonld be read with this correction therein that the samemay conform to the record of the case in the Patent Office.

Signed and sealed this 26th day of April, A. D. 1958.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents;

